During hemodialysis, the dialysate sodium concentration plays a role in patient outcomes. Performing hemodialysis on a patient with specific dialysate sodium ion concentrations can influence the occurrence of hypotensive episodes, the prevention of disequilibrium syndrome, and the minimization of interdialytic weight gain, among other things. Methods and systems to manage sodium dialysate concentration are important with systems that contain a component that may change the sodium ion level to unknown values. For example, regenerative hemodialysis systems, such as the Recirculating Dialysate System (“REDY” System), contain sorbent materials that release and/or remove sodium from the dialysate fluid. The removal and/or addition of sodium to the dialysate fluid depend on several factors including: patient blood urea level, patient weight, dialysate composition, sorbent properties, etc. Because of this, it becomes difficult to predict the changes in dialysate sodium concentration that will occur during a hemodialysis session.
Expensive sorbent materials can be depleted, and also necessitate complicated management systems to monitor sodium concentration of the dialysate fluid exiting the sorbent system. For example, the “REDY” system requires 6 to 8 liters of water for operation and in some cases the patient is required to remove 1 to 2 liters of dialysate during operation and replace with 1 to 2 liters of fresh water in order to reduce the sodium levels in the dialysate. Increases in sodium ion concentration of a working dialysate become difficult to predict during hemodialysis treatment. As such, there is a need for eliminating system components that contribute to increases in sodium ion concentrations. There is also a need for a system having reduced sodium levels in the dialysate fluid prior to entering a regenerative dialysate system such that the amount of sodium released by a sorbent system is low. There is a related need for systems and methods that do not require sodium control or only require simplified or minimal management. Further, there is a need for systems and methods that can control the sodium concentration of the dialysate by removing or adding sodium ions from a working dialysate. There is also a need for methods for managing sodium that minimize system size and weight and do not require large amounts of water.
In addition to being in danger of exposure to the complications of unknown sodium levels during dialysis sessions, some kidney patients can experience an extreme variation of potassium levels during their dialysis sessions that increases their health risk. During hemodialysis, there is a net addition of base in the form of bicarbonate, which increases the cellular uptake of potassium and attenuates the overall removal of potassium from the cells. Hence, patients may initially experience an increase in their intracellular potassium levels followed by a reduction in levels resulting in hypokalemia. This condition is of particular concern to patients with underlying cardiac conditions. As such, there is an unmet need to guard against risk to patients during dialysis sessions by monitoring potassium and more tightly controlling potassium levels, as well as to more efficiently manage sodium levels. There is also a need for methods and systems to determine the potassium dialysate concentration, particularly where the dialysis system itself contains a component that affects the potassium concentration in the dialysate fluid.